It's the last paragraph: "Google supports mRSS, [...]"; mRSS is a link to <a href="http://search.yahoo.com/mrss" rel="nofollow">http://search.yahoo.com/mrss</a> -- it seems like it should do a search, but it 404s to the Yahoo homepage.
It's probably like that because mRSS was developed by Yahoo + mRSS community <a href="http://en.wikipedia.org/wiki/Media_RSS" rel="nofollow">http://en.wikipedia.org/wiki/Media_RSS</a>